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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 6 Dec 2019 19:50:08 -0800
Message-ID: <CAHk-=wizsHmCwUAyQKdU7hBPXHYQn-fOtJKBqMs-79br2pWxeQ@mail.gmail.com>
Subject: Re: [PATCH 0/2] pipe: Fixes [ver #2]
To:     David Sterba <dsterba@suse.cz>,
        David Howells <dhowells@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Eric Biggers <ebiggers@kernel.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Fri, Dec 6, 2019 at 1:04 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> It doesn't fix my "kernel compiles go single-threaded" issue.

I ended up just bisecting it.

The "make goes slow" problem bisects down to b667b8673443 ("pipe:
Advance tail pointer inside of wait spinlock in pipe_read()").

I assume it's the added "do_wakeup = 0" (not the spinlock) that ends
up having some subtle issue.

Very strange, but there it is.

               Linus